DNA damage in kidney transplant patients. Role of organ origin

Chronic kidney disease (CKD) patients are characterized by elevated levels of genomic damage. This damage increases when kidney function decreases being maximum in hemodialysis patients. As kidney transplantation improves renal function, and it is related with better survival, the aim of our study was to evaluate potential changes in DNA damage levels after kidney transplantation, and comparing living donor recipients with cadaveric donor recipients. The alkaline comet assay was used to determine DNA breaks and oxidative damaged DNA; and the micronucleus assay was used to determine chromosomal breakage and/or aneuploidy. Fifty CKD patients were followed up after 6 and 12 months of their kidney transplantation. All patients increased their genomic damage levels after 6 and 12 months of renal transplantation, compared with those observed before transplantation, despite of the improvement of their metabolic functions. Donor advanced age correlated positively with higher DNA damage. Genomic damage was lower in living donor transplants with respect to cadaveric donor transplants. Our conclusion is that DNA damage increased in kidney transplantation patients, whereas their renal function improved. Higher levels of DNA damage were found in cadaveric donor transplants when compared to living donor transplants. Environ. Mol. Mutagen. 58:712–718, 2017. © 2017 Wiley Periodicals, Inc.     

Genomic instability in chronic renal failure patients

Patients suffering chronic renal failure (CRF) exhibit a high incidence of cancer, as well as high levels of genetic damage. We hypothesized that these patients show genomic instability as measured by increased radiosensitivity to the induction of genetic damage. The background levels of genetic damage and the net genetic damage after in vitro irradiation with 0.5 Gy were analyzed using the micronucleus assay in peripheral blood lymphocytes of 174 CRF patients and 53 controls. The net radiation‐induced genetic damage was significantly higher in CRF patients with respect to controls. Among CRF patients, the levels of genetic damage were higher in those with prior incidence of cancer than in those without cancer; in addition, those CRF patients undergoing hemodialysis presented with higher levels of genetic damage than those in the advanced Stages (4–5) of the pathology. A positive association was observed between basal and net micronucleus frequency among CFR patients. However, no association was found between net genetic damage and parameters linked to the different stages of the pathology, such as urine creatinine levels and glomerular filtration rate. Our results indicate that CRF patients show increased radiosensitivity and that the degree of radiosensitivity is associated with the progression of the pathological stage of the disease. Environ. Mol. Mutagen., 2012. © 2012 Wiley Periodicals, Inc.     

sTREM‐1 in patients with chronic kidney disease on hemodialysis

The triggering receptor expressed on myeloid cells‐1 (TREM‐1) is a member of the immunoglobulin superfamily. TREM‐1 has been implicated as an amplifier of inflammation. Soluble TREM‐1 (sTREM‐1) was investigated in different clinical conditions, but not in hemodialysis (HD) patients. We aimed to investigate sTREM‐1 as a marker of inflammation in HD patients. We investigated 40 CKD patients undergoing chronic HD treatment and 15 controls. Routine laboratory investigations in addition to CRP measured by immunoturbidimetry, TNF‐ α, and sTREM‐1 measured by ELISA were assayed in post–hemodialysis patients’ blood samples and in controls’ blood samples. CRP, TNF‐α, and sTREM‐1 levels were significantly higher in HD patients than in controls (p < 0.001 for all). sTREM‐1 was positively correlated with CRP and TNF‐α (r = +0.50, p < 0.001 and r = +0.53, p < 0.001 respectively). It was negatively correlated with hemoglobin concentration (r = ?0.69, p < 0.001). Hemoglobin concentration was the significant predictor of sTREM‐1 level (p < 0.001). In conclusion, sTREM‐1 level is significantly increased in HD patients as are other pro‐inflammatory markers.     

IL‐2/IL‐6 ratio correlates with liver function and recovery in acute liver injury patients

Acute liver injury can result from a number of different diseases. Inflammatory cytokines are known to be involved in the development of this condition; however, their precise roles and effects on liver function remain unclear. The goal of this study was to determine the relationship between serum cytokine levels and both the severity of liver damage and recovery in acute liver injury. We enrolled 100 patients with acute liver injury caused by drug application who were hospitalized from September 2012 to September 2017 and measured serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and the cytokines, interleukin (IL)‐2 and IL‐6, before and after clinical therapy. Our results indicate that IL‐2 and IL‐6 levels are altered significantly following clinical therapy. However, with the exception of an association between IL‐2 and ALT, we found no correlation between the differences in cytokine levels pre‐ and post‐therapy and recovery of liver function. In contrast, we observed that pre‐ vs post‐treatment difference in the IL‐2/IL‐6 ratio negatively correlates with the pre‐ vs post‐treatment difference in ALT and AST values, and positively correlates with ALT and AST at 1‐month post‐discharge. Thus, our data suggest that IL‐2/IL‐6 ratio may represent a novel predictor for the prognosis of liver injury.     

Time in hemodialysis modulates the levels of genetic damage in hemodialysis patients

It is assumed that hemodialysis treatment can diminish the levels of genetic damage in circulating lymphocytes by cleaning the blood of uremic toxins that cause oxidative stress. However, the hemodialysis process by itself may also induce genomic damage by producing reactive oxygen species (ROS). We conducted a follow‐up study in a group of 70 hemodialysis patients followed for a mean time of 15 months. We investigated the effect of exposure time in hemodialysis on the levels of genetic damage in peripheral blood lymphocytes using the micronucleus assay. In addition, genetic damage after in vitro irradiation with 0.5 Gy was also analyzed to evaluate changes in radiosensitivity. Our results showed that, at the end of the study, there was a decrease in both the basal levels of genetic damage (9.9 ± 1.0 vs. 7.6 ± 0.7) and radiosensitivity values (38.5 ± 3.0 vs. 27.6 ± 2.4). We conclude that hemodialysis procedures may act as an ameliorating factor reducing the genetic damage present in chronic kidney disease patients. Environ. Mol. Mutagen. 55:363–368, 2014. © 2014 Wiley Periodicals, Inc.     

Prognostic impact of 8‐hydroxy‐deoxyguanosine and its repair enzyme 8‐hydroxy‐deoxyguanosine DNA glycosylase in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has a poor prognosis in the setting of chronic inflammation and fibrosis, both of which promote nuclear DNA oxidative damage. 8‐hydroxy‐deoxyguanosine (8‐OHdG) DNA glycosylase (OGG1) enhances the repair of 8‐OHdG, which is the primary oxidative stress‐induced mutation that leads to malignant alterations. This study aims to clarify the relationships between oxidative stress‐induced factors and HCC progression. The clinicopathological factors were compared with immunohistochemistry OGG1 and 8‐OHdG expressions in 86 resected HCC specimens. High 8‐OHdG expression was associated with high serum aspartate transaminase and total bilirubin levels, as well as a low platelet count, compared with low 8‐OHdG expression. Histological liver cirrhosis and poor differentiation were more frequent in patients with high 8‐OHdG expression than in those with low 8‐OHdG expression. The 8‐OHdG was negatively correlated with OGG1 expression in HCC patients. Therefore, we classified the patients into two groups, low OGG1/high 8‐OHdG group and the other group. The patients with low OGG1/high 8‐OHdG expressions had worse prognosis than those with the other expressions. Our results showed that low OGG1/high 8‐OHdG expressions in nuclei influence HCC patient outcomes. Evaluating the patterns of OGG1 and 8‐OHdG expressions might provide pivotal prognostic biomarkers in patients with HCC.     

Influence of Carnicor,Venofer, and Sevelamer on the levels of genotoxic damage in end‐stage renal disease patients

End‐stage renal disease (ESRD) patients present high levels of phosphorus and calcium products in serum, which contribute to the development of vascular calcification and cardiovascular disease, and to low iron stores and carnitine deficiency. For these reasons, ESRD patients are generally supplemented with different medicines. Some of the most common treatments include the use of Carnicor, Venofer, and Sevelamer drugs. Carnicor is used as a source of L‐carnitine, acting as antioxidant and neuroprotector. Venofer is used to reduce the deficit of iron. Sevelamer is used to treat hyperphosphatemia. To determine the potential harmful genotoxic effects of these drugs, a group of 214 patients included in a hemodialysis program with different intakes of Carnicor, Venofer, and Sevelamer were evaluated. The levels of basal and oxidative DNA damage, as well as chromosomal damage, were measured in all individuals using the comet and the micronucleus assays, respectively. Our results indicate that Carnicor administration was associated with low but significant increases in the frequency of basal DNA damage and micronuclei. Environ. Mol. Mutagen. 59:302–311, 2018. © 2018 Wiley Periodicals, Inc.     

Increased exhaled H2O2 and impaired lung function in patients undergoing bioincompatible hemodialysis

BACKGROUND: Chronic renal failure (CRF) and hemodialysis (HD) accumulate an inflammatory milieu, contributing to increased systemic and airway oxidative stress that may lead to lung damage. OBJECTIVES: This study was designed to assess exhaled hydrogen peroxide (H2O2), lung function and whole blood chemiluminescence in HD and CRF patients and healthy controls. METHODS: The study included 59 patients (Polyamide STM or Hemophan membranes--19, cuprophane--16, hemodiafiltration--14, continuous ambulatory peritoneal dialysis--10), 16 CRF and 16 healthy controls. The assessment of lung function included FVC (forced vital capacity), FEV1 (forced expiratory volume in the first second) and DLCOc (single breath CO diffusing capacity). Exhaled H2O2 was determined fluorometrically and resting and n-formyl-methionyl-leucyl-phenylalanine (fMLP) luminol-dependent whole blood chemiluminescence (LBCL) were measured simultaneously. RESULTS: Only cuprophane HD patients presented decreased lung function (FVC 63.8+/-17.4%, FEV1 55.9+/-20.3 and DLCOc 72.1+/- 9.3 % of predicted; p<0.05 vs. controls). These patients exhaled the highest H2O2 levels in comparison to CRF (p<0.01): median 0.36 microM (range R: 0.09-0.56 microM) and controls (p<0.05): 0.17 microM (0.2-17.8 microM). These levels were not decreased during the HD session: preHD 1.25 microM (0.2-16.5 microM) and postHD 1.3 microM (0.2-17.8 microM). As a marker of systemic oxidative stress, fMLP-induced LBCL (total light emission) was increased in these patients (1570.6 aUxs/10(4) phagocytes; R: 274.2-8598.9) and in the CRF group (2389.4 aUxs /10(4) phagocytes; R: 491.5- 6184; p<0.05 vs. controls). Other patient groups did not express elevated LBCL and revealed decreased exhaled H2O2 after a session. CONCLUSIONS: An increased oxidative burden in the lungs may contribute to functional lung impairment in patients dialyzed with a cellulose membrane. Biocompatible dialysis with other modalities might reduce airway-borne oxidative stress and is not related with lung damage.     

How the Duration Period of Erythropoietin Treatment Influences the Oxidative Status of Hemodialysis Patients

Background: End-stage renal disease is a state of enhanced oxidative stress (OS) and hemodialysis (HD) and renal anemia further augment this disbalance. Anemia correction with erythropoietin (EPO) may improve oxidative status. However, there is no evidence of time dependent effects of EPO therapy on redox status of HD patients.Objective: The aim of this study was to evaluate whether the duration of EPO treatment may affect OS parameters in uremic patients.Patients and methods: 104 HD patients and 29 healthy volunteers were included. Patients were divided into 3 groups according to the duration of EPO treatment. Forth group consisted of HD patients without EPO treatment. Plasma and erythrocyte malondialdehyde (MDA, MDA_rbc), reactive carbonyl groups (RCG), plasma sulfhydryl (-SH) groups and total antioxidative capacity (TAC) levels were evaluated.Results: HD patients both with and without EPO treatment, showed a significant increase in all oxidative parameters without significance between EPO treated and -untreated group. The decrease in MDA and MDA_rbc levels coincided with the duration of EPO treatment. A negative correlation was observed between the duration of EPO treatment and serum MDA (r=˗0.309, p=0.003). Increasing periods of EPO treatment were associated with decrease in RCG, without significance between EPO groups. Increase in TAC accompanied increasing durations of EPO treatment, with EPO treatment for more than 24 months causing the most striking changes (p<0.05). There were no significant differences in ˗SH levels between EPO subgroups.Conclusion: Our results suggest that long term administration of EPO attenuated the lipid peroxidation process and restored the levels of antioxidants.     

Cardiovascular risk in hemodialysis patients: a mechanistic approach

A new formula is proposed to express the excess burden of cardiovascular risk faced by hemodialysis patients as a function of various inherent, acquired and potentially modifiable factors. The proposed equation CVR(HD) = CVR(B) X f(([CKD+HD]/[HD(tech)+Dr])+X) includes the terms: CVR(HD) (cardiovascular risk in hemodialysis patients); CVR(B) (baseline cardiovascular risk); CKD (risk associated with chronic kidney disease); HD (risks associated with the process of hemodialysis); HD(tech) (benefits of new hemodialysis technologies); Dr (benefits of drug therapies) and X (unknown or putative factors influencing cardiovascular morbidity). We review the various factors included in this proposed formula, touching upon the epidemiology, pathophysiology and therapeutic implications, including possible strategies to modify risk. As is apparent from the formula, CKD and HD in particular act as risk multipliers in augmenting or amplifying the baseline cardiovascular risk, while new hemodialysis technologies may provide an opportunity for "cardioprotective dialysis". Drug treatment may serve to mitigate some of the risk unique to this population.     

8OHdG levels in brain do not indicate oxidative DNA damage in Alzheimer''s disease

Accumulation of oxidative DNA damage has been proposed to underlie aging and neurodegenerative diseases such as Alzheimer's Disease (AD). The DNA adduct 8-hydroxy-2′-deoxyguanosine (8OHdG) is considered a good indicator of oxidative DNA damage. To investigate whether this type of DNA damage is involved in AD etiology, 8OHdG levels were determined in postmortem human brain tissue of controls and AD patients (in frontal, occipital, and temporal cortex and in hippocampal tissue). Parametric studies in rat revealed no influences of postmortem delay, repeated freezing/thawing or storage time. In human brain, approximately two 8OHdG molecules were present per 10⁵ 2′-deoxyguanosines. In AD patients and controls, 8OHdG-levels were not related to age, sex, or brain region. Also, no differences were found between controls and AD patients. It was concluded that 8OHdG in nuclear DNA, although present throughout the brain in fairly high amounts, does not accumulate with age, nor does it appear to be involved in AD. More detailed studies are required to extend this conclusion to other types of oxidative damage.     

DNA damage and repair capacity in workers exposed to low concentrations of benzene

DNA damage and cellular repair capacity were studied in 18 male fuel tanker drivers and 13 male filling‐station attendants exposed to low and very low concentrations of benzene, respectively, and compared to 20 males with no occupational exposure (controls). Exposure to airborne benzene was measured using passive personal samplers, and internal doses were assayed through the biomarkers t,t‐muconic acid, S‐phenylmercapturic acid and urinary benzene. DNA damage was evaluated using tail intensity (TI) determined by the comet assay in peripheral lymphocytes. Urinary 7‐hydro‐8‐oxo‐2’‐deoxyguanosine (8‐oxodG) was measured as a biomarker of oxidative damage. DNA repair kinetics were assessed using the comet assay in lymphocytes sampled 20 and 60 min post H₂O₂ exposure. Benzene exposure differed significantly between the drivers (median 246.3 µg/m³), attendants (median 13.8 µg/m³), and controls (median 4.1 µg/m³). There were no differences in TI and 8‐oxodG among the three groups, or between smokers and non‐smokers. DNA repair kinetics were similar among the drivers, attendants and controls, although the comet assay on H₂O₂‐damaged lymphocytes after 60 min revealed significantly lower levels of TI only in drivers. The DNA repair process in smokers was similar to that observed in drivers. In conclusion, this study found no relationship between low levels of benzene exposure and DNA damage, although there was evidence that exposure interferes with DNA repair kinetics. The biological impact of this finding on the onset of genotoxic effects in exposed workers has still to be ascertained. Environ. Mol. Mutagen. 57:151–158, 2016. © 2015 Wiley Periodicals, Inc.     

Abnormal mitochondrial dynamics, mitochondrial loss and mutant huntingtin oligomers in Huntington's disease: implications for selective neuronal damage

The purpose of our study was to determine the relationship between mutant huntingtin (Htt) and mitochondrial dynamics in the progression of Huntington's disease (HD). We measured the mRNA levels of electron transport chain genes, and mitochondrial structural genes, Drp1 (dynamin-related protein 1), Fis1 (fission 1), Mfn1 (mitofusin 1), Mfn2 (mitofusin 2), Opa1 (optric atrophy 1), Tomm40 (translocase of outermembrane 40) and CypD (cyclophilin D) in grade III and grade IV HD patients and controls. The mutant Htt oligomers and the mitochondrial structural proteins were quantified in the striatum and frontal cortex of HD patients. Changes in expressions of the electron transport chain genes were found in HD patients and may represent a compensatory response to mitochondrial damage caused by mutant Htt. Increased expression of Drp1 and Fis1 and decreased expression of Mfn1, Mfn2, Opa1 and Tomm40 were found in HD patients relative to the controls. CypD was upregulated in HD patients, and this upregulation increased as HD progressed. Significantly increased immunoreactivity of 8-hydroxy-guanosine was found in the cortical specimens from stage III and IV HD patients relative to controls, suggesting increased oxidative DNA damage in HD patients. In contrast, significantly decreased immunoreactivities of cytochrome oxidase 1 and cytochrome b were found in HD patients relative to controls, indicating a loss of mitochondrial function in HD patients. Immunoblotting analysis revealed 15, 25 and 50 kDa mutant Htt oligomers in the brain specimens of HD patients. All oligomeric forms of mutant Htt were significantly increased in the cortical tissues of HD patients, and mutant Htt oligomers were found in the nucleus and in mitochondria. The increase in Drp1, Fis1 and CypD and the decrease in Mfn1 and Mfn2 may be responsible for abnormal mitochondrial dynamics that we found in the cortex of HD patients, and may contribute to neuronal damage in HD patients. The presence of mutant Htt oligomers in the nucleus of HD neurons and in mitochondria may disrupt neuronal functions. Based on these findings, we propose that mutant Htt in association with mitochondria imbalance and mitochondrial dynamics impairs axonal transport of mitochondria, decreases mitochondrial function and damages neurons in affected brain regions of HD patients.     

Modulation and source of procalcitonin in reduced renal function and renal replacement therapy

Serum procalcitonin (PCT), an accurate marker of severe infection, is moderately increased in chronic kidney disease (CKD), peritoneal dialysis (PD) and haemodialysis (HD). We studied the extent of PCT elevation and factors accounting for elevated PCT in CKD and dialysis, and whether peripheral blood mononuclear cells (PBMC) contribute to increased PCT. In 37 controls, 281 CKD, 31 PD, and 65 HD patients without infection, PCT was measured and correlated with CKD stage, PD, HD, C-reactive protein (CRP), cardiovascular disease (CVD) and other clinical parameters. PCT release by PBMC from controls, advanced CKD, PD and HD patients (12 subjects each) was measured. PCT increased in parallel to the deterioration of CKD. Oliguria, advanced CKD, PD, HD, CVD and elevated CRP were independently associated with PCT elevation. PCT release from PBMC significantly increased in advanced CKD, PD and HD. PCT release from PBMC correlated closely with the corresponding serum PCT values (r=0.76, P <0.001). In the absence of infection, PCT may increase due to reduced renal elimination and increased synthesis, as due to PBMC. Furthermore, serum PCT could serve as a marker of low-grade inflammation and CVD, which substantially increase mortality in CKD and dialysis.     

血透患者血浆中选择素P水平的变化

采用双抗体夹心法（ELISA）,定量测定20例慢性肾功能不全维持性血透患者（HD）透析过程中血浆选择素P水平的动态变化。结果显示:HD组血浆选择素P水平在透析前与正常对照组无明显差异（P>0.05）,而透析后5min选择素P即显著升高,并随透析过程逐渐升高（P<0.01～0.001）。同时观察到透析后白细胞计数下降、提示血透过程中血小板被激活,血小板与白细胞粘附的增加。     

Hemodialysis Affects Phenotype and Proliferation of CD4-Positive T Lymphocytes

CD4⁺ T lymphocytes of patients with chronic kidney disease (CKD) are characterized by reduced levels of crucial surface antigens and changes in the cell cycle parameters. Recombinant human erythropoietin (rhEPO) normalizes their altered phenotype and proliferative capacity. Mechanisms leading to the deficient responses of T lymphocytes are still not clear but it is postulated that immunological changes are deepened by hemodialysis (HD). Study of activation parameters of CD4⁺ T lymphocytes in hemodialyzed and predialysis CKD patients could bring insight into this problem. Two groups of patients, treated conservatively (predialysis, PD) and hemodialyzed (HD), as well as healthy controls, were included into the study; neither had received rhEPO. Proportions of main CD4⁺CD28⁺, CD4⁺CD25⁺, CD4⁺CD69⁺, CD4⁺CD95⁺, and CD4⁺HLA-DR⁺ lymphocyte subpopulations and proliferation kinetic parameters were measured with flow cytometry, both ex vivo and in vitro. No differences were seen in the proportions of main CD4⁺ lymphocyte subpopulations (CD4⁺CD28⁺, CD4⁺CD25⁺, CD4⁺HLA-DR⁺, CD4⁺CD69⁺, CD4⁺CD95⁺) between all examined groups ex vivo. CD4⁺ T lymphocytes of HD patients exhibited significantly decreased expression of co-stimulatory molecule CD28 and activation markers CD25 and CD69 after stimulation in vitro when compared with PD patients and healthy controls. HD patients showed also decreased percentage of CD4⁺CD28⁺ lymphocytes proliferating in vitro; these cells presented decreased numbers of finished divisions after 72 h of stimulation in vitro and had longer G0→G1 time when compared to healthy controls. CD4⁺ T lymphocytes of PD patients and healthy controls were characterized by similar cell cycle parameters. Our study shows that repeated hemodialysis procedure influences phenotype and proliferation parameters of CD4⁺ T lymphocytes.     

尿毒症及透析患者血浆IL-1β、TNFα、IL-6水平及其意义

目的　研究尿毒症状态和血液透析对血浆细胞因子的影响。方法　应用酶联免疫吸附分析(ELISA)方法检测正常人、尿毒症未透析患者、腹膜透析患者和应用铜仿膜、聚砜膜、聚甲基丙烯酸甲酯膜(PMMA)血液透析患者血浆IL-1β、TNFα、IL-6水平。结果　尿毒症未透析患者血浆TNFα、IL-6水平显著高于正常对照(P<0.05)。在应用不同透析膜15分钟时,血浆细胞因子水平较透析前有不同程度的降低,聚砜膜透析时IL-1β、TNFα降低明显,统计学差异显著(P<0.05)。应用三种透析膜透析时细胞因子无显著性差异。结论　尿毒症未透析状态可导致激活外周血单核细胞(PBMC)产生细胞因子,不同透析膜透析时激活PBMC及吸附、清除细胞因子的程度不同,单纯用细胞因子的血浆水平变化来评价透析膜的生物相容性存在一定局限性。     

Effects of Zinc Supplementation on Plasma Copper/Zinc Ratios,Oxidative Stress,and Immunological Status in Hemodialysis Patients

Background: Patients undergoing hemodialysis (HD) have low plasma levels of zinc (Zn), high plasma levels of copper (Cu), and exhibit increased oxidative stress, inflammation, and immune abnormalities. We evaluated the effects of Zn supplementation on abnormal plasma Cu/Zn ratios and clinical outcomes in HD patients.Design and Methods: Patients on long-term HD with lower than normal plasma concentrations of Zn (< 80 mg/dL) were randomized to receive daily oral Zn supplements (n = 40) or no supplements (n = 25) for eight weeks. Age- and sex-matched healthy individuals served as a control group (n = 38). A number of clinical parameters were measured before and after the supplementation period.Results: Compared with healthy subjects, patients had significantly elevated plasma Cu concentrations and Cu/Zn ratios, as well as higher levels of oxidative stress and pro-inflammatory cytokines. Patients who received Zn supplements for eight weeks had higher plasma concentrations of Zn and lower concentrations of Cu, along with reduced Cu/Zn ratios, oxidative stress status, and inflammatory responses compared to patients who did not receive Zn. Patients receiving Zn also showed significantly higher percentages of CD4 and CD19 lymphocytes, and elevated CD4/CD8 ratios.Conclusions: Zn supplementation ameliorates abnormally high plasma Cu/Zn ratios and may reduce oxidative stress, improve inflammatory status, and maintain immune function in patients undergoing long-term HD.     

DNA damage in leukocytes of workers occupationally exposed to arsenic in copper smelters

Inorganic arsenic (i-As) is a known human carcinogen; however, humans continue to be exposed to i-As in drinking water and in certain occupational settings. In this study, we used the Comet assay to evaluate DNA damage in the somatic cells of workers from three Polish copper smelters who were occupationally exposed to i-As. Blood samples were collected from 72 male workers and 83 unexposed male controls and used for the detection of DNA damage, oxidative DNA damage, and DNA damage after a 3-hr incubation in culture. Urine samples were collected to assess the level of exposure. The mean concentration of arsenic metabolites in urine [the sum of arsenite (AsIII), arsenate (AsV), monomethylarsenate (MMA) and dimethylarsenate (DMA)] and the concentrations of DMA (the main metabolite in urine) were higher in workers than in controls, but the differences were not statistically significant. By contrast, the level of DNA damage, expressed as the median tail moment, was significantly higher in the leukocytes of workers than in the controls. Comet assays conducted with formamidopyrimidine glycosylase (FPG) digestion to detect oxidative DNA damage indicated that oxidative lesions were present in leukocytes from both the exposed and control groups, but the levels of damage were significantly higher among the workers. Incubation of the cells in culture resulted in a significant reduction in the levels of DNA damage, especially among leukocytes from the workers, suggesting that the DNA damage was subject to repair. Our findings indicate that copper smelter workers have increased levels of DNA damage in somatic cells, suggesting a potential health risk for the workers. Although i-As was present in air samples from the smelters and in urine samples from workers, no clear association could be made between i-As exposure and the DNA damage.